A precision crystal phase-matching angle metrology instrument

Abstract An instrument has been developed to measure the optimal phase-matching angle of large-aperture potassium dihydrogen phosphate (KDP) crystal. KDP crystal in the frequency converter is applied to generate a third harmonic generation, which is important to achieve inertial confinement fusion (ICF). To achieve high harmonic conversion efficiency, the tuning angle of KDP crystal should be optimal when the frequency converter is working online in ICF facilities. The optimal tuning angle of KDP crystal must be measured off-line before KDP crystal is mounted in the facility. The Crystal Phase-matching angle Metrology Instrument (CPMI) can measure the optimal phase-matching angle and harmonic conversion efficiency of KDP crystal off-line. The CPMI is housed in ISO 5 clean room and several methods are taken to keep the temperature stable. The automatic alignment system is built in the CPMI which makes the measurement convenient and fast. The working posture adjustment system is applied to measure the optimal phase-matching angle when KDP crystal is in the working posture. The integration control system is assisted to measure the phase-matching angle automatically, which can increase the work efficiency immensely. Some experiments are done to test the measuring accuracy. The experiments indicate that the measuring error does not exceed 10 μrad and the repeated accuracy does not exceed 3 μrad. The CPMI can replace on-line measuring of the optimal phase-matching angle, which is economical and time-saving.